Mars Volta is an unbelievable band - again I'm going to side with Sheep on this one and say that comparisons are for the birds. Unless you're trying to describe to someone what a band sounds like you may give them indications by offering comparisons, but in the case of Tool, Mars Volta, and quite a bit of Mike Patton's post-Faith No More work for example, they are all so unique and descript in their own respects that comparisons do nothing but undermine their value.
Much of what you hear on the radio from Tool is their mid-90's "hits" if you want to call them that, and IMO, a far cry from their best material. 10,000 days is an epic album start to finish.